Think and think again. Two history-engaging, European-inflected, cerebral yet very material shows in New York right now take Conceptualism from the droll (Marcel Broodthaers) to the slapstick (Fischli/Weiss), with various stops along the way. It’s the thinking person’s workout—philosophical, political, ironic, and often fun.

On view at the Museum of Modern Art is the late Belgian artist, poet, experimental filmmaker, Surrealist master-crafter of mussel-shell art, and deadpan humorist Marcel Broodthaers’s meticulously compiled mental and visual arsenal. Words and formulas are rendered minimally and elusively on paper and in films, as well as concretely, with texts and objects embedded in plaster, giving sculptural solidity to words and thoughts, as in Pense-Bête (Memory Aid), 1964.

In their Guggenheim show “How to Work Better,” Peter Fischli and David Weiss extract oddities from such mediums as clay, video, photographs, found objects, and film in a brilliant union of high and low art. Living dangerously, courting failure, reveling in disorganization and contradiction, and simply playing, the duo excitedly explore the history of everything, from ancient art to mechanics to film to the nature of materials and animals.

Like Fischli/Weiss, who were left-wing anarchic, ebulliently nihilistic, Broodthaers was political, often ironically, but also very directly. He produced Le Problème noir en Belgique (The Black Problem in Belgium), 1963–64, a construction consisting of a newsprint story headlined “The Congo Must Be Saved.” The article, on Belgium’s former colony, is topped with shiny black-painted eggshells that seem to ooze onto the paper, suggesting fertility and death. There’s beauty in the work’s glowing richness and horror in its evocation of race and blood.

In other like-minded works, Broodthaers applied fragile white eggshells, like text, to a painted ground divided into black, yellow, and red, the colors of the Belgian flag; he composed huge pots of mussels; and he made “paintings” with the shells as medium. These symbols were his national identity, his sustenance, and the substance of his art—and they’re economical.

On the one hand, fragility engenders unease, and cracked eggs suggest what might have emerged—dead or alive. Assemblages like La Grand-Mère (The Grandmother), 1964, a hilarious gathering within an oval frame of eggshells containing a mussel shell, a bicycle pump, and a brush for hair evoking Meret Oppenheim, form a Dadaist homage to portraiture and a dig at tradition.

As self-appointed director of his own museum—the Musée d’Art Moderne, Département des Aigles (Museum of Modern Art, Department of Eagles)—Broodthaers included in its displays not artworks so much, but documents, publications, films, and financial records. Operating as both institutional critique and an actual exhibiting museum—the installation, on view here in several rooms, traveled in various forms and remained functioning until 1972.

Similarly—in a way—the dynamic Swiss duo Fischli and Weiss, the latter of whom died in 2012, render the world and its contents as a universe of parody, wry reflection, and slapstick action. As with Broodthaers, they have deep roots in literature, art, history, and film. They all conjure up Beckett, Buster Keaton, and of course Charlie Chaplin, in photos and films. And they call to mind Rube Goldberg in their absurdist constructions in action that unravel, trip, tumble over themselves, and smash to the ground. There’s science and fake science at play, including experiments with mini explosions and burned cardboard sculptures.

Fischli/Weiss take parodic punches in their evocations of pre-Columbian art in affecting homages to humble materials like unfired clay. An overabundance of little sculptures is densely installed on the Guggenheim’s ramp looking like freshly dug-up archeological finds. Their titles are literary and hilarious, as when they allude to the most sophisticated figures and ideas in history, such as Mr. and Mrs. Einstein Shortly after the Conception of Their Son, the Genius Albert. Here, they depict the dad and mom nestled cozily in their beds. And there’s a crowded little tableau, titled Galileo Galilei Shows Two Monks That the World Is Round, rolling a big ball in their midst.

Running throughout their work is the concept of “Popular Opposites.” Fischli/Weiss render absurdities and impossibilities, such as making large entities small and vice versa.

Their alter egos Rat and Bear—costumes acquired in L.A. for their early movie-making ventures—were adopted as disguises and poignant symbols of absurdity and vulnerability. Spread out on a blanket in the rotunda, the two equal-size costume figures welcome visitors to a world of sloth, warmth, and reckless irresponsibility.

The great unresolvable admonition on Fischli and Weiss’s “How To Work Better” list (printed on their public sculpture) sums it all up, insisting DISTINGUISH SENSE FROM NONSENSE. Neither they nor Broodthaers can or do so. Thank goodness.

“Marcel Broodthaers: A Retrospective” is on view at the Museum of Modern Art in New York through May 15.

“Peter Fischli David Weiss: How to Work Better” is on view at the Guggenheim Museum in New York through April 27.